Recent years have seen music delivery using high-resolution sound sources, audio data having a sound quality exceeding that of music-use CDs (Compact Discs) (CD-DA (Compact Disc Digital Audio)).
In music delivery using a digital signal delta-sigma modulated by a one-bit signal (hereinafter also referred to as a DSD (Direct Stream Digital) signal), not only a DSD signal that is 64-fold the CD sampling frequency of 44.1 kHz (64DSD signal) used for Super Audio CD (SACD) but also a DSD signal that is 128-fold the CD sampling frequency (128DSD signal) and a DSD signal that is 256-fold the CD sampling frequency (256DSD signal) are experimentally delivered.
DSD signal is higher in sampling frequency than PCM (Pulse Code Modulation) signal, resulting in a larger communication capacity than for PCM signal in the case of streamed delivery. Assuming, for example, that a stereo (two-channel) signal is used and that it is three seconds a frame, the data capacity of a 64DSD signal is approximately 2.8 Mbits/frame.
On the other hand, for example, a technology is available that stores, in advance, a plurality of pieces of coded data that represent the same content at different bit rates in a content server such as MPEG-DASH (Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (HyperText Transfer Protocol)) so that a client apparatus receives a desired piece of coded data by streaming from among the plurality of pieces of coded data to match with a network communication capacity (e.g., NPL 1).
In music delivery using DSD signals, it is also possible to dynamically select a DSD signal of better quality for listening, for example, from among signals of the same content having different bit rates such as 64DSD, 128DSD, and 256DSD signals to match with the communication circuit capacity by using a streaming technique such as MPEG-DASH.
When a desired DSD signal is selected from among a plurality of DSD signals having different sampling frequencies for switching to the selected signal, a method for achieving smooth switching is proposed, for example, in PTL 1.